Method for making a dry shaver blade



April 2s, 1964 J. F. WAHL METHOD FOR MAKING A DRY SHAVER BLADE Pol FiledNOV. 30, 1961 FIG, 7

IN V EN TOR. John f' Wahl C'zys United States Patent O 3,130,609 NETHGDFR MAKNG A DRY SHAVER BLADE John F. Wahl, Sterling, Iii., assigner toWahl lipper Corporation, Sterling, lil., a corporation of Illinois FiledNov. 30, 1961, Ser. No. 156,101 3 Claims. (Cl. *7e-lill) This inventionrelates to a method for making a dry shaver blade, and more particularlyto a method for making a curved shaver blade wherein the cutting edgesof the blade project beyond t e blade surface which defines averageblade curvature.

It has been found that the cutting action of dry shaver blades andoverall shaver efficiency can be improved substantially by having thecutting edges of the fixed and movable cutting blades contact each otheron as small a total area as possible. ln addition to providing morepositive cutting action, this arrangement minimizes the sliding frictionbetween the blades and thus enables the use of smaller and lessexpensive motors. Further, the arrangement provides a more efcient useof the available bias or pressure which necessarily is used between theblades to give desired cutting action.

By way of example, the method of this invention is illusnated anddescribed in connection with making a curved outer blade, ie. thestationary blade or comb, of a dry shaver. The blade made by theillustrated method is perforated, and it is intended to be mounted inthe shaver in such a way that at least the perforated portion is curved.

A curved outer blade made in accordance with the method of thisinvention has cutting edges which project inwardly beyond the insidecurved surface of the blade, and it is these cutting edges which engagethe outside curved surface of the associated inner movable blade of thedry shaver. These projecting cutting edges are located at opposite sidesof the perforations in the outer blade and they extend in a directionwhich is generally normal to the direction of movement of thereciprocating inner blade. As will be seen, these inwardly projectingcutting edges are easily and economically formed by using the method ofthis invention.

Other objects, advantages and details of the invention will be apparentas the description proceeds, reference being had to the accompanyingdrawing which illustrates various aspects and steps of the invention. itwill be understood that the description and drawing are illustrativeonly and that the scope of the invention is to be measured by theappended claims.

ln the drawing:

FiG. l is a plan view of a partially formed blade member used in themethod of the invention;

FIG. 2 is a perspective view of a completed blade showing the curvatureof the blade when mounted for use in a dry shaver;

FIG. 3 is a perspective view of a partially formed blade showing thecurvature given to the blade preparatory to the step of lapping theinside surface;

FIG. 4 is a transverse sectional view of a lapping rod in operativerelation with a partially formed blade, the blade being supported in aresilient back-up means which also is shown in section;

FIG. 5 is an enlarged sectional view showing the relationship betweenthe lapping rod and a partially formed blade at the initiation of thelapping step;

FlG. 6 is a fragmentary enlarged plan view of the inside surface of ablade made by the method of this invention; and

HG. 7 is a fragmentary longitudinal sectional view showing therelationship in a dry shaver between an outer blade made by the methodof this invention and a cooperating inner blade.

3,130,609 Patented Apr. 28, 1964 ice Referring to the drawing, FIG. 1shows a partially formed blade 14) used in the method of this invention.Blade 10 is an initially at, thin sheet of metal. Although the method ofthis invention advantageously can be used with metal which is notprehardened, it is preferable for obvious reasons to use prehardenedstock.

Side portions 11 and 12 of blade 10 respectively engage the dry shaverwhen the blade is curved as shown in FIG. 2 and mounted in the shaver.Side portion 11 has apertures 13 and 14 which receive projectionsextending from one side of the shaver and side portion 12 has apertures15 and 16 for projections extending from the other shaver side.

The central portion of blade 10 is provided with suitable hair receivingperforations 18 which, as shown in FIG. 6, may be generally elongated.The perforations, however, may be round, or of other desired shape.Perforations 18 as illustrated are arranged in rows, with theperforations in one row being staggered with respect to the perforationsin adjacent rows. In addition, the illustrated rows are parallel andinclined at a small angle to the blade ends 19 and 2@ (FIG. vil).

FIG. 2 shows a finished blade curved to the shape possessed by the bladewhen mounted in a shaver. The inside surface of the blade is designated22. The blade shown in FIG. 2 is curved about an axis 25, and at leastthe perforated part of the blade is generally concentric with this axis.It will be noted that the projected directions of the rows ofperforations and the long dimensions of the individual perforations (ifelongated) are approximately at right angles or normal to axis 2S.

The characterizing aspect of the illustrated method resides in the stepof lapping in a novel manner the inside surface 22 of the partiallyformed blade 10. As will be seen, blade 10 is lapped in a directionwhich is at an approximate angle of degrees to the direction in whichblades of this type customarily are lapped. Thus, the present lappingstep might be termed cross lapping.

FIG. 3 shows the manner in which blade 10 is curved preparatory to thelapping, or cross lapping, step. The blade is curved in the samedirection as the curvature employed in mounting the blade, but it iscurved on an axis 27 which is approximately at right angles or normal tothe axis 25 about which the blade is curved when mounted in a shaver.Thus, as illustrated in FIG. 3, the rows of perforations in the blade ascurved for lapping extend parallel to the curvature axis 27. The radiusof curvature given to blade 10 during the lapping step by the lappingrod is preferably generally the same or slightly smaller than the radiusof curvature used when the blade is mounted in a shaver. Within limits,the smaller the radius of the lapping rod, the more pronounced are theinwardly projecting cutting edges, as will be seen.

Referring to FIG. 4, the curved blade 10 is supported in a resilientback-up means 3@ which may reciprocate as indicated by the arrow 31. Asshown, back-up means 30 may comprise a metal or wood plate 32 covered bya layer 33 of resilient material such as sponge rubber. The lapping stepis carried out with a lapping rod 34 which reciprocates longitudinallyor rotates, or both reciprocates and rotates.

As shown in enlarged FIG. 5, the blade metal extending transverselybetween perforations 18 of curved blade 1), which metal constitutesteeth 35, deviates somewhat from the average surface of curvature. Theblade metal adjacent the edges of perforations 18 stands away oroutwardly from the surface of average blade curvature which isrepresented generally by the surface of lapping rod 34.

From the foregoing it will be understood that as the lapping stepproceeds, less metal is removed from teeth edges 38 (FIGS. 5 and 6) thanis removed from elsewhere on inner surface 22 of blade 10.

In other Words, referring to FIG. 5, the arcuate surface of lapping rod34 is effective to remove more metal from central portion 37 -of teeth35 and elsewhere than is removed from teeth edges 38. Thus, after thelapping step is completed, teeth edges 38 project inwardly beyond animaginary arcuate surface defined by the portions of the blade surfacefrom which the greater amount of metal has been removed.

FIG. -6 is an enlarged fragmentary plan View of the innersurface 22 ofthe blade after completion of the lapping step. The shaded areas 38adjacent the long edges of perforations 18 indicate those portions ofthe blade surface where less metal is removed than elsewhere in vthecourse of the lapping step. These edges 38 constitute the cutting edgesof teeth 35.

As previously mentioned, a blade made by the foregoing method is curvedto the shape shown in FIG. 2 when mounted in a shaver. The axis of thiscurvature is, of course, approximately at right angles or normal to thecurvature axis used during the lapping step.

FIG. 7 is a fragmentary enlarged sectional view of a fixed outer bladecurved above axis 25 (FIG. 2) to the shape it possesses when mounted ona shaver. For illustrative purposes FIG. 7 also shows in section aninner movable blade 46 in effective relation with fixed outer blade 10.It will be noted that edges 38 of teeth 35 .project inwardly andconstitute the portions of blade 10 which mainly engage the outersurface of inner movable blade 40.

Teeth edges 38 constitute the cutting edges of blade 10 land therelationship thereof with movable blade 40 in- The relationship alsosures improved cutting action. minimizes sliding friction between theblades and thus enables the use of smaller and less expensive motors.

.In addition, the relationship provides a more eicient use of theavailable cutting bias which necessarily is provided between the bladesto give desired cutting action.

From the above description it is thought that the procedures andadvantages of the invention will be readily apparent to-those skilled inthe art. Various changes in detail may be made without departing fromthe spirit or losing the advantages ofthe invention.

VHaving .thus described the invention, what I claim as new and desire tosecure-by Letters Patent is:

`1. The method for making a curved outerblade for a dry shavercomprising the steps of curving said sheet on an axis generally parallelto said rows whereby the metal along the long edges of said perforationsstands outwardly from the surface of average sheet curvature, said sheetengaging resilient back-up means;

lapping the interior of said sheet with a lapping rod having generallythe said average curvature whereby less metal is removed from said sheetalong the long edges of said perforations than elsewhere; and

curving said sheet with the perforated portion of the sheet curved on anaxis generally normal to the axis of curvature used during the lappingstep whereby the metal along the long edges of said perforationsprojects inwardly beyond the surface of average sheet curvature toprovide cutting edges.

2. The method for making a dry shaver blade comprising the steps of:

curving a thin sheet of perforated metal about a first axis wherebymetal at perforation edges generally parallel to said axis standsoutwardly from the surface of average sheet curvature;

lapping the interior of said sheet with a lapping rod having generallythe said average curvature whereby .less metal is removed from saidsheet at said perforation edges than elsewhere; and

curving said sheet with the perforated portion curved on a second axisgenerally normal to said first axis whereby the metal at saidperforation edges projects inwardly beyond the surface of average sheetcurvature to provide cutting edges.

3. The method for making a dry shaver blade comprising the steps of:

resiliently supporting a thin sheet of perforated metal against acylindrical lapping tool whereby metal at perforation edges generallyparallel to the axis of said tool stands outwardly from the surface ofaverage sheet curvature;

lapping the interior of said sheet whereby less metal is removed fromsaid sheet at said perforation edges than elsewhere; and Y curving saidsheet with the perforated portion curved on an axis generally normal tothe axis of said tool whereby metal at said perforation edges projectsinwardly beyond the surface of average sheet curvature to providecutting edges.

References Cited in the file of this patent UNITED STATES PATENTS1,246,996 Pfeifer Nov. 20, 1917 1,900,158 Butler Mar. 17, 1933 2,182,067Bruecker Dec. 5, 1939

1. THE METHOD FOR MAKING A CURVED OUTER BLADE FOR A DRY SHAVER COMPRISING THE STEPS OF: SELECTING AN INITIALLY FLAT, THIN, RESILIENT PREHARDENED SHEET OF METAL; PERFORATING SAID SHEET WITH ROWS OF ELONGATED HAIR RECEIVING PERFORATIONS, THE PERFORATIONS IN ADJACENT ROWS STAGGERED; CURVING SAID SHEET ON AN AXIS GENERALLY PARALLEL TO SAID ROWS WHEREBY THE METAL ALONG THE LONG EDGES OF SAID PERFORATIONS STANDS OUTWARDLY FROM THE SURFACE OF AVERAGE SHEET CURVATURE, SAID SHEET ENGAGING RESILIENT BACK-UP MEANS; 